東南アジア巨大都市縁辺部の土地自然・土地利用変化とその適正化 ―メトロマニラ郊外市街地における事例研究―

要旨

In large Southeast Asian cities, urban green spaces are continuously decreasing due to rapid urbanization. Consequently, serious environmental problems are being experienced, and it is urgently necessary to develop appropriate landscape plans for these cities. This case study was conducted to better understand the present situation of green spaces in Marikina City, located in the suburbs of metropolitan Manila, a typical example of a large Asian city. To obtain information for future landscape planning, the study also examined the factors affecting the green spaces. The changes of land use and green spaces in relation to the urbanization process were investigated through the examination of aerial photographs. GIS was used for data analysis.
Land-use changes progressively advanced according to the ease of development as affected by landform. Urbanization proceeded on all types of landforms, and as a consequence, green spaces significantly decreased in all land uses. Residential area was the most quickly expanding land use, reflecting the fact that urbanization will continue because of the ever-increasing population. Green spaces in individual residential lots seem to be very important, however.
A vegetation survey was conducted in residential districts of Marikina City, and the quantitative and qualitative characteristics of trees were analyzed. Lot size has some influence on the quantity of greenery in residential lots. In smaller lots, however, quantity did not increase in proportion to lot size. It appears, then, that the land-use controls for individual lots did not function effectively. Residential lots developed before rapid urbanization had more greenery than those developed in recent years. The quantitative difference of greenery has some relation with the qualitative difference of greenery, depending on the year or period of development of the residential area. In the old residential lots, the greenery is composed mostly of fruit trees, which have a practical use. In the newly developed residential lots, however, the greenery is comprised mostly of ornamental trees.
Under the present circumstances, there is no assurance of sustaining the desired quantity of greenery in smaller residential lots. In the future, planners should promote consensus building with local residents about the conservation and creation of green spaces on their private lands as well as enhance land-use control.